Over the course of a 5-K run, the average runner strikes the ground about 3,000 times, placing ground reaction force loads of 2 to 3 times the body weight on each leg and sending shock waves through the feet, legs, spine, and elsewhere. Because of this repetitive high-impact loading, many injuries are associated with running. The injuries can include “runner's knee” (pain in the knee), Shin splints, bone stress fractures, plantar fasciitis, and Achilles tendinitis. Repetitive stress in the same tissues/bones without enough time for recovery or running with improper form can lead to such injuries.
The advice generally given to runners to attempt to avoid such injuries is to warm up before exercising, use cross training with different speeds/distances/exercises as part of an exercise routine, run-on softer surfaces, use high-quality cushioned running shoes, and to replace running shoes often. Because the cushioning provided by running shoes wears out over time, avid runners are generally advised to replace running shoes every six months. In view of the high cost of quality running shoes, runners are presented with a dilemma of balancing the replacement cost of shoes with essentially a guesstimate as to when a particular pair of running shoes no longer provides sufficient cushioning and should be replaced before injury. Once a pair of shoes is replaced, it generally is never used again for running, although it may still provide sufficient cushioning for running on softer surfaces, such as on treadmills, gravel/dirt, or grass.
Consequently, there continues to be a tremendous need for further innovation that can assist runners with avoiding preventable injuries while enabling more cost effective use of running shoes.